Bill Gates has spent much of his career trying to excite customers, shareholders and analysts about Microsoft Corp. This week, he turned his attention to getting college students excited about the field of computer science.

At MIT, where Gates made the fourth of five stops on a weeklong college tour Thursday, he recalled the early excitement of the computer revolution when he was a student just up the road at Harvard. He tried to persuade students there are still exciting academic and practical challenges in the field.

"It's not yet the machine that we envisioned in terms of ease of use or the breadth of things to be done," Gates said of the computer. "But we have a good rough draft."

It may seem a curious message to take to MIT, a campus that's as wired as any and is bursting with talented young programmers who will soon be working in the field. But even at MIT, the appeal of studying pure computer science has dwindled recently. The number of computer science majors is down about 30 percent in the last three or four years, said John V. Guttag, head of the school's electrical engineering and computer science departments.